Qiwen Du,Weichen Jia,Jingyu Dai,Chao Du,Aiyun Shao,Rongmin Zhang,Yuefei Ji
Natural organic matter (NOM) contains a large number of aromatic ketones and quinones, which can produce reactive oxygen species (ROS), such as 1 O 2 and HO·, through photosensitization. These ROS play important roles in the attenuation of organic pollutants in sunlit surface water. The NOM components fractionated with XAD-8 resin at different pH influence the photo-generation of ROS, which may be related to the degree of dissociation of functional groups. In this study, probe chemicals were used to investigate the effect of dissociation degree (p K a ) of NOM model compounds on ROS production under 254 nm UV irradiation. Experimental results showed that six model compounds with similar molecular weights and structures but different p K a values have different ROS production abilities in a pH 7.0 reaction system. The ability for DHB 2,5 (2.97), DHB 3,4 (4.48), and GUA (9.99) to photo-generate 1 O 2 increased with increasing dissociation. The ability for DHB 3,4 and GUA to photo-generate HO· followed the same trend. The correlation between NOM dissociation constant and ROS generation is preliminary established, which explains the influence of functional groups. Our results may provide some basic information for understanding the correlation between NOM structural features and ROS generation.
Zhendong Fu,Feng Guo,Jiahe Qiu,Runchi Zhang,Mingxu Wang,Liping Wang
2-Methylimidazole (MIM) is a classic organic ligand that shows excellent thermal stability and chemical robustness and is widely used in ZIFs. Recently, transformations of MOFs have been realized by using metals or ligands. In this study, we propose a new strategy—adjusting MIM by extending the alkyl chain length —to change the properties of related MOFs. Furthermore, we used copper as the metal core to replace zinc to mimic the active sites of laccases (electron transfer between copper and imidazole ring). As a result, the nanostructures transformed from nanoleaves to nanovesicles, which changed the Cu(II)/Cu(I) ratio from 3.7 to 1.7, as well as the lattice constant (decreased the diffraction angle) and enzyme-like activity (inhibition). In addition, we revealed that superoxidase anions were the main factors responsible for its laccase-like activity. We applied it to detect and discriminate phenolics. Laccase-mimicking activity was best at pH 7.0. When compared to protein laccase, the Cu-MeIm nanozyme had a greater Vmax at the same mass concentration. It was used to identify and distinguish phenolics. In the presence of Cu-MeIm nanozymes, the linear range is 0.1–2 mM and the detection limit of 2,4-DCP is 0.034 mM.
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